WITHDRAWN (NO SHOW) SF05.10.01 Smart Materials with Tunable Properties Based on Low Melting Point Alloys

Smart materials with tunable properties such as mechanical stiffness and electrical conductivity have ample applications in soft robotics as actuating and sensing units. These smart materials typically are achieved through polymer-matrixed composite structures containing conductive reinforcement components. The stiffness change typically is realized through phase change of the reinforcement or glass transition of the matrix. Low melting point alloys (LMPA) in the form of layers and long fibers have been recently used in composite structures with tunable stiffness due to its low energy barrier for activation and high electrical conductivity.<br/><br/>In this talk, we explore the possibility to disperse LMPA into a polymer matrix to achieve robust smart materials with highly tunable properties. In the first approach we start with an LMPA foam with randomly distributed interconnected pores, and then infiltrate the LMPA foam with uncured elastomer such as polydimethylsiloxane (PDMS) to form a robust bicontinuous foam composite with stiffness change of three orders of magnitude. In the second approach we mix both LMPA particles and conductive fibers into an elastomer matrix to form a percolative network of particles and fibers within the matrix, such that the resultant smart materials have tunable electrical conductivity and mechanical stiffness. Recognizing the lack of appropriate analytical models for the mechanical and electrical properties of these smart materials, we have used effective medium theory informed by microstructure information to estimate their stiffness and electrical conductivity. Our experimental and modeling results are in good quantitative agreement. We also demonstrate the superior performance of these novel smart materials based on LMPA foam and LMPA particles in soft robotics applications.